A means employed up to the present in producing inductors in thin-film circuits consists in using films comprising conductor tapes rolled in spirals and fixed to the surface of the circuit board. As a rule, the spiral covers a square area, for convenience in using the surfaces of the board. The value of these inductors is low, namely a few microHenrys, owing to the mediocre magnetic permeability of the surrounding zone (substrate and air).
Further, it has not yet been possible to incorporate into printed circuit boards, electronic devices employing transformers, such as stabilised power supplies, and such incorporation is of course even less feasible with integrated circuit supports. These transformers have therefore had to be provided as discrete units of by no means negligible bulk and weight, as compared with the degree of microminiaturization attained in printed and, even more so, in integrated circuit technology.
The purpose of the invention is the creation of inductive circuits, such as self-inductors, transformers, and relays, which are incorporated into the substrates of printed or integrated circuits.